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ITO E RO E K SOP No.026,REV.1 ASSOCIATES,INC INDOOR AIR AND SUB-SLAB SOIL GAS SAMPLING METHODS PAGE 12 • Laboratory-provided identification numbers for SUMMA® canisters and/or regulators; • Any problems encountered during sample collection; and • Pre- and post-condition of the sampling location and/or project site. 2.5 DUPLICATE AND EQUIPMENT BLANK COLLECTION Based on the requirements of the QAPP/FSP, quality control (QC) samples may need to be collected. This may include ambient air and equipment blank samples. These QC samples should be collected from an upwind portion of the facility, preferably during the collection of a soil gas sample. Record ambient air PID readings at 5-minute intervals. Place two canisters equipped with regulators (timeframe of collection specified in the FSP) on ground surface in an upwind location. For ambient air sample, attach the regulator directly to the canister and open the valve. For the equipment blank,attach a length of tubing (approximately the same length as that to be used during subsurface soil gas sample collection,tightened only 1/8 turn past finger tight) and direct push sample collection fitting representative of that used for soil gas sample collection to the other canister/regulator.The intake portion of the canister only (ambient air) and equipment blank assembly should be located as close to one another as is possible. Open both sample collection valves simultaneously. Record valve opening time and initial vacuum for each canister. Collect samples for the time specified in the QAPP/FSP. Close valves on both canisters simultaneously, taking care not to allow the canister to reach atmospheric pressure. Record the sample collection end time and canister vacuum for each canister. If a duplicate sample is required, drill a second hole through the slab approximately 6 inches from the proposed sampling location. Follow all the procedures described in Section 2.3 above. After setting up the sampling systems, ensure that both sample collection valves are opened simultaneously. Duplicate soil gas samples will be collected at each site as required in the site-specific QAPP/FSP. Generally, one duplicate sample will be collected for every ten samples collected.